An Internet meme is a cultural artifact that spreads rapidly, reaching a very large digital audience within a short period of time. Because internet memes spread through online communities much like a disease spreads through an offline population, they are also referred to as viral content.

Memes are often puzzling, humorous, entertaining or inspiring. The infectious content is often delivered through images or video files but a meme can also be simply text. Like its biological counterpoint, a meme often mutates along the way, changing to meet the needs of its audience.

In the early days of the internet, memes were spread through email and discussion forums and they could take weeks or months to reach a large audience. Today, when a meme is spread through social media share channels, it can reach a worldwide audience within a day — or even hours.

Once an internet meme has reached critical mass, it often crosses over into other popular media and is spread even farther through coverage on television, in newspapers and in magazines. Conversation about the meme becomes, in effect, a fad. Like other types of fads, however, the life of an internet meme is often brief and its popularity fades as the content loses its novelty. There are, however, some memes that have had so much impact on popular culture, they’ve become classic.

Leetspeak – the substitution of a word’s letters with numbers or special characters was inspired by military jargon and made popular by programmers in the 1980’s. Some of today’s chat acronyms and emojis have their roots in leetspeak.

LOLcats — posting images of cats with semi-literate captions, such as “I can has cheezeburger?” has been popular since 2006. Mutations of this meme include dog shaming — posting images of canines with signs around their necks explaining the pets’ misdeeds.

RickRoll – hyperlinks that are purposely misdirected to a video of 80’s pop star Rick Astley singing “Never Gonna Give You Up” have been reported since 2008. A similar prank sends website visitors to a video of Russian singer Eduard Khi singing “Trololo.”

25 random things about me – a Facebook list meme that has been popular since 2009.

Evolutionary biologist Richard Dawkins coined the term meme in his 1976 book, “The Selfish Gene.” As conceived by Dawkins, a meme is a unit of culture that is passed from one generation to another and correlates to the unit of physical heredity, the gene. Some psychologists maintain that internet memes are the result of a collective obsession. By definition, a collective obsession has three main characteristics: it spreads quickly, it is viewed as ridiculous by people who do not share the obsession and once it peaks, it loses popularity quite quickly.

Marketers, hoping to take advantage of the grass roots aspect of internet memes, have sought to harness the power of the social phenomenon by creating viral marketing campaigns intended to promote a particular brand, product or service and monetize social buzz. Despite advances in big data analytics, however, predicting what content will go viral and become a meme is an impossible task.